The invention is related to a wheel brake for a vehicle comprising a brake disc unit adapted to brake the rotation of a rotation element, which is adapted to be drivingly connected to the wheel, wherein the brake disc unit comprises a first set of discs and a second set of discs arranged in an alternating manner in an axial direction, wherein the discs in said first disc set are adapted to be rotationally rigidly connected to said rotation element. The invention also relates to a vehicle comprising the wheel brake.
This type of disc brake is commonly used at each wheel of a work vehicle. The term “work vehicle” comprises different types of material handling vehicles like construction machines, such as a wheel loader, an articulated hauler, a backhoe loader, a motor grader and an excavator. Further terms frequently used for work vehicles are “earth-moving machinery” and “off-road work machines”. The work vehicles are for example utilized for construction and excavation work, in mines etc. The invention will be described below in a case in which it is applied in an articulated hauler. This is to be regarded only as an example of a preferred application. The invention may, for example, also be used in other heavy vehicles such as trucks and buses.
The discs in the first disc set are rotationally rigidly-connected to the rotation element and displaceable along their centre axis. The discs in the second disc set may be stationary, e.g. by being connected to the housing of the brake. More precisely the discs in the second disc set are prevented from rotation around their centre axis but are also displaceable along said centre axis. Upon activation of the brake disc unit the stationary discs are forced towards each other by means of an activation means, such as a piston, or the like, wherein the intermediate discs of the first disc set are clamped. The free distance between two adjacent discs from different sets of discs, or from the same set of discs, is not definite when the brake disc unit is deactivated. The discs are solely allowed to diverge upon deactivation by retracting the activation means, but the diversion of the discs is not controlled.
When the brake disc unit is deactivated (retraction of the activation means) after a braking operation, the discs may in some situations not be totally separated from each other, but may instead stay in contact with each other. Further, when the vehicle is operated on a sloping ground, the brake disc unit will be tilted and the discs may be displaced towards each other due to gravity and come into contact with each other. A work vehicle is frequently used to transport heavy loads from one location to another, often encountering varying grade slopes on the route between two or more locations. If the discs are in contact during propulsion they are subject to considerable wear, at the same time as the generation of heat is increased. This leads to a higher need of cooling by lubricating oil, a higher fuel consumption and a more frequent maintenance.
It is desirable to achieve a wheel brake which creates conditions for a more efficient energy consumption of the vehicle during operation. The invention especially aims for a wheel brake, in which the discs are efficiently separated when the wheel brake is in the deactivated condition.
According to an aspect of the invention, the brake disc unit comprises at least one separator element, which is adapted to keep a sufficient distance between two adjacent discs of one of the disc sets for an intermediate disc from the other disc set to rotate at least substantially freely relative to the spaced discs when the brake disc unit is in a deactivated condition. In other words, the intermediate disc is at least substantially free from frictional contact with the adjacent, spaced discs when the brake disc unit is in the deactivated condition. In other words, two adjacent discs from different disc sets may rotate freely relative to one another. The separator element is preferably adapted for keeping a predetermined distance between the adjacent discs when the brake disc unit is in the deactivated condition. The separator element may either be adapted for spacing stationary brake discs or rotation brake discs (friction discs) and the intermediate disc may either be a stationary disc or a rotation disc.
According to a preferred embodiment, said separator element is variable between a first state, in which the intermediate disc may rotate at least substantially freely relative to the adjacent spaced discs, and a second state, in which the intermediate disc is clamped between the adjacent discs of the other disc set. Thus, the separator element is in the first state when the brake disc unit is in the deactivated condition and in the second state when the brake disc unit is in the activated condition.
According to a further preferred embodiment, the separator element has a larger axial extension than the intermediate disc in the first state, and at least as small axial extension as the intermediate disc in the second state. Preferably, the separator element is resilient in order to adopt the first and second state, wherein the separator element is adapted to have a larger potential energy in the second state than in the first state.
According to a further preferred embodiment, the separator element extends from one of the discs. In this way, no additional device is required for the separation, which creates conditions for reducing the material cost and the assembly work needed. Preferably, the separator element forms a unitary part with one of the discs.
According to a further preferred embodiment, the separator element is positioned at the outer periphery of the associated disc. Thus, the separator element is adapted to bridge the gap between the two adjacent discs in the same disc set and abut the neighbouring disc in a space efficient way.
According to a further preferred embodiment, a plurality of separator elements are circuxnferentially spaced along the associated disc. An efficient separation of the two adjacent discs is achieved in this way.
Further preferred embodiments and advantages will be apparent from the following description and drawings.